Viruses – both real and virtual – have a lot in common. For starters, they both suck to catch. Smallpox, Stuxnet, Conficker, or the common cold – we can all agree that regardless of whether they're in your body or your PC, viruses are universally awful. Second of all, while both types of viruses can be avoided with the proper precautions, odds are you'll still pick one up at some point in your life. And lastly, just like recognizing a viral infection in your body, knowing if your PC has been infected is all about knowing the symptoms. So, as netizens concerned for the well-being of the community, we've put together this list of computer virus symptoms to help you diagnose any problems you might be experiencing.

Telltale signs of an infected PC

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Remember these things? Dear god were they annoying back in the day. One minute you're minding your own business, talking with your buddy through this newfangled online chatroom thingy, and then BAM! a flashy window appears to inform you that you're millionth visitor to this site, and you absolutely must CLICK HERE TO CLAIM YOUR PRIZE!

Luckily, those days are behind us. Most modern browsers now include robust popup blockers, so pop-ups shouldn't really be a problem anymore if your browser is up to date. The occasional pop up might still happen if you're clicking around a shady site, but it's highly unlikely nowadays that you'll encounter a lot of them online. If you're getting a lot of pop-ups while you're surfing the Web, it's likely just a poorly-configured browser. Adjust your settings and they should go away.

What you should really worry about is if you're still getting pop-ups while your browser isn't even open. If that's the case, chances are good that you have a virus on your system. The most common ones are ads that say something like "Alert! your computer might be infected with a virus," and then offer up free software to fix it. Please don't be a numbskull and fall for this – you'll only be downloading more malware.

Hijacked accounts and messages you didn't send

Just like real-world viruses, computer viruses are on a mission to spread and infect as many machines as possible, and often the way they do this is by hijacking your email, IM, or social media accounts and sending malware-laden messages to your contacts. This is hard to detect sometimes, since most of us keep a close watch on our inboxes, but rarely stop to check our outboxes. More often than than not, you find out about these phantom messages from your savvy friends who see them in their inbox, realize something's phishy, and let you know you might've been hacked. Just keep an eye on your Sent messages on every platform and make sure you change your account password if you notice anything you didn't write yourself.

Lockdown warnings

So you're on your PC, doing your thing and putting the finishing touches on the most adorable kitten GIF of all time. Suddenly, an official-looking message appears on your screen, informing you that your computer has been locked due to your illegal activity, and that you must pay a fee to regain control of it. Don't worry, these types of messages are complete bull. You weren't doing anything illegal – kitten GIFs are not illegal! – your computer is just infected with ransomware.

Sometimes these messages aren't even official-looking; they're just plain old ransom notes that say, "we've taken control of your computer, pay us and we'll let it go free." Whatever you do, do not enter any kind of payment information. Chances are slim that it'll give you back control. What's worse is that you probably won't be able to remove the virus with your normal antivirus software either – you'll need to get your hands on a rescue disc from AVG or Kaspersky.

Crashing, freezing, and general slowness

While system crashes, frozen screens, and painfully slow operation could be caused by poor configuration, these can sometimes also indicate that your PC is infected with malware. The best way to tell if it's one or the other is how quickly things got bad. If your computer has gradually been getting slower over time and has now reached a point where it occasionally comes to a halt, it might be simply because you haven't been performing regular system maintenance. Check out our guide to speeding up your PC to help speed things back up.

If your computer was running smoothly one day, and suddenly became laggy, slow, and unresponsive overnight, then there's a chance that malicious software is the cause. Viruses often run tasks that take up a lot of resources and make your system run more slowly than usual. Try opening up Task Manager to see what's running. If that doesn't work, keep reading.

Essential functions don't work

Most major operating systems come standard with a task manager that allows you to see what your PC is doing at any given moment. For Windows users, this can be accessed with control+alt+delete, whereas Mac users can simply open Spotlight (command+space) to find/open the Activity Monitor program. These tools will provide you insight into what programs are currently running on your computer, and you should always be able to access them. If for some reason you can't get your task manager (or other diagnostic tools) to open, there's a chance your computer is infected with a virus that doesn't want you to find it.

If this happens, run your antivirus program if you can. If you can't (presumably because the virus is blocking this too), then you'll likely have to resort to a separate virus removal tool.

Nothing's wrong

Even if everything seems peachy and your computer runs without any problems, there's always the chance that your system is harboring a malicious piece of software that you're totally unaware of. As a general rule, the more advanced the virus, the lower your likelihood of discovering the infection. Think about it – if you were a world-class cybercriminal, would you design a virus that people could easily detect and shut down, or would you take time to make it practically invisible? Exactly.

Some of the most sophisticated viruses in the world have been found to include software that actually deletes other malicious files that might get cause virus scanners to send up red flags. As cybercriminals continue to step up their game, it's increasingly likely that you won't even notice your computer has a virus, so keeping this in mind, you shouldn't always assume that you aren't infected simply because your system runs smoothly. At the end of the day, the best way to keep your PC malware-free is to give it regular checkups with a good antivirus program, and always make sure that your operating system is up to date.

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